Grab bucket operating apparatus

ABSTRACT

A grab bucket operating apparatus in which the half shells of the bucket are mounted on individual torque shafts, each of the torque shafts is provided with a lever and a hydraulic unit is operatively connected to one of the levers, and a link member connects the levers to ensure synchronous opening and closing of the half shells, and an accumulator ensures maintenance of hydraulic pressure in the hydraulic circuit, and electric and hydraulic controls are provided for the operating mechanism.

United States Patent [191 Taguchi et a1.

[ GRAB BUCKET OPERATING APPARATUS [75] Inventors: Masahiro Taguchi, Katsushika-ku,

Tokyo; Tetsuo Sasaki, Shinagawa-ku, Tokyo, both of Japan [73] Assignee: Algoship International Limited,

Nassau, Bahamas [22] Filed: Mar. 9, 1972 [21] Appl. No.: 233,114

[30] Foreign Application Priority Data Feb. 25, 1971 Japan 46/11920 May 26, 1971 Japan 46/36097 [52] US. Cl 294/70, 37/187, 294/88 [51] Int. Cl. B66c 3/02 [58] Field of Search 294/69, 70, 71, 88, 294/106; 37/183 R, 186, 187, 188; 214/147 [56] References Cited UNITED STATES PATENTS Billings 294/71 Nov. 27, 1973 3,310,335 3/1967 Shuey 294/88 3,048,288 8/1962 Dwyer 214/147 G 3,413,029 11/1968 Donovan 4 294/70 FOREIGN PATENTS OR APPLICATIONS 1,481,745 3/1969 Germany 294/70 Primary ExaminerEvon C. Blunk Assistant ExaminerJohnny D. Cherry Attorney-Robert Duncan et a1.

[5 7] ABSTRACT A grab bucket operating apparatus in which the half shells of the bucket are mounted on individual torque shafts, each of the torque shafts is provided with a lever and a hydraulic unit is operatively connected to one of the levers, and a link member connects the levers to ensure synchronous opening and closing of the half shells, and an accumulator ensures maintenance of hydraulic pressure in the hydraulic circuit, and electric and hydraulic controls are provided for the operating mechanism,

18 Claims, 7 Drawing Figures PATENTEnnnvm I975 33; 774354 I SHEET 5 OF 5 bucket started to be lifted kg /,E 160 2 F 14o 2 kg, |G 70 2 bucket starts I 4 l x z bucket is comto close T pletely closed effecti.ve hydraulic energy cylinder stroke in second GRAB BUCKET OPERATING APPARATUS This invention relates to grab bucket operating apparatus and particularly to grab buckets operated by electro-hydraulic means, and incorporating a hydraulic accumulator adaptable for use in all types of operations where loose material is handled.

In the conventional electrically and hydraulically operated bulk-material grab bucket, it is opened or closed by a hydraulic power cylinder into which is forced the hydraulic energy or working liquid under pressure supplied from a pump with a fixed discharge capacity or fixed stroke pump through a flow direction switching valve which is electrically actuated so that the adjustment of the grab bucket closing or opening time has been impossible and the closing or opening time remains constant without changing the pump and hydraulic cylinder.

Therefore, the bulk-material loading and discharging operation is limited in time depending upon the types of the bulk materials and the loading and discharging locations, and is not efficient. To overcome this problem there has been proposed a method in which a large capacity pump is employed so as to supply a large quantity of working oil per time unit into a hydraulic cylinder to increase the volume of bulk materials to be loaded or discharged per time unit. However, an electric motor with a greater capacity must be employed and a capacity of an oil tank must be increased so that the weight of the grab bucket is inevitably increased. The result is that the volume of the bulk materials to be loaded and discharged by the grab bucket is, of course, reduced and the power consumption is inevitably increased. Furthermore, the cabtyre cables having a greater diameter must be used so that a drum for winding the cabtyre cables must have a greater torque. Thus it is seen that the efficiency of a grab bucket with a fixed opening and closing time is very low and that if the-shorter opening and closing time is desired, the manufacturing and maintenance costs are inevitably increased. Furthermore, the standardization of the driving parts and accessories is difficult.

The present invention was made to overcome the problems associated with the prior art and provides an improved electrically and hydraulically operated grab bucket. The apparatus includes a center frame incorporating lever driving mechanisms such as an electric motor,'a hydraulic pump, a hydraulic cylinder. Necessary connections and valves are fitted in the hydraulic circuit for operation of the apparatus. A pair of torque shafts are supported, in parallel relation preferably on the underside of the center frame, preferably in split journals located at the four corners of the frame. A lever on each of the torque shafts are connected together by a rod and one of the levers is connected to the piston rod of the hydraulic cylinder. A grab bucket shell is mounted on each of the torque shafts for rotation therewith when the hydraulic cylinder is reciprocated.

A hydraulic accumulator is inserted in the hydraulic cylinder circuit in such a Way that the hydraulic energy from the pump is accumulated in the hydraulic accumulator when the grab bucket is not being opened or closed and the accumulated hydraulic energy is supplied to the hydraulic cylinder which serves to open and close said grab bucket.

The object of the invention is, therefore, to provide a grab bucket operation mechanism which will be simple and inexpensive to manufacture and operate.

A further object of the invention is to provide a grab bucket operating mechanism which can be adapted for different end uses by replacing one type or size of bucket shells for another.

A further object of the invention is to provide a grab bucket operating mechanism in which an accumulator is maintained at operating pressure by a motor driven pump when the grab bucket is not being opened or closed.

A still further object of the invention is to provide timing mechanism whereby the operation of the switching valve and the pump in a grab bucket operation apparatus is controlled to adjust the pressure in an accumulator in conjunction with the speed of lifting and lowering the apparatus.

These and other objects of the invention will be apparent from the attached drawings in which:

FIG. 1 is a perspective view of a grab bucket operating apparatus according to the present invention.

FIG. 2 is a vertical section of the grab bucket operating apparatus shown in FIG. 1.

FIG. 3 is a vertical section taken on the line 3-3 of FIG. 2.

FIG. 4 is a view similar to FIG. 3, but showing an arrangement using two cylinder and piston devices.

FIG. 5 is a hydraulic circuit diagram for the grab bucket operating apparatus.

FIG. 6 is an electric circuit diagram for the grab bucket operating apparatus.

FIG. 7 is a graph illustrating the relationship between the stroke in time of a hydraulic cylinder on the one hand and the force exerted by the grabbed bulk materials in the prongs or teeth of the grab bucket, and the hydraulic pressure in a hydraulic accumulator.

Referring to the drawings, the grab bucket 5 comprises a center frame head unit 6 and a pair of grab bucket shells 7 and 8 mounted for rotation on and with the torque shafts 9 and 10.

The torque shafts 9 and 10 are each journalled in a pair of split bearings 11 and 12 located on the under surface of the head unit 6 at the corners thereof. The grab bucket shell 7 is secured on the shaft 9 while the grab bucket shell 8 is secured on the shaft 10.

The grab bucket shells 7 and 8 illustrated are for illustrative purpose only and will be designed for any particular end use desired.

A lever 13 is secured on the torque shaft 9 and projects upwardly through a slot 14 in the under surface of the bottom wall 15 of the head unit 6. A lever 16 is secured to the torque shaft 10. A tie rod 17 is connected at one end to the lever 16 by the pin 18 and at the other end to the lever 13 by the pin 19 at the point intermediate the length of the lever 13.

A hydraulic cylinder 20 is pivotally mounted on the pin 21 located within the head unit 6 at the end thereof adjacent the torque shaft 10 and the end 22 of the piston rod 23 is pivotally connected to the pin 24 on the end of the lever 13 remote from the torque shaft 9.

An electric motor 25 and drivably connected hydraulic pump 26 are mounted on the bottom wall 15 of the head unit 6, and an accumulator 27 is mounted on the side wall 28 within the head unit 6. Suitable electrical and pipe connections and control valves, as shown in diagrammatic form in FIGS. 5 and 6, are installed between the motor, pump, accumulator and cylinder 20 for the operation of the grab bucket 5 from a remote location.

The grab bucket is suspended from any suitable crane or derrick by means of the eyebolt 29 affixed on the cover 30.

Referring now particularly to FIG. 2, the distance L between the axis of the torque shaft 9 and the pin 19 is made equal to the distance L between the torque shaft 10 and the pin 18.

When the levers 13 and 16 are positioned as shown in FIG. 2, and the piston rod 23 of the hydraulic cylinder 20 is extended, the bucket is closed, as shown in FIG. 1. When the piston rod 23 of the hydraulic cylinder 20 is retracted by means of the motor operating the hydraulic pump 26 while maintaining fluid pressure in the accumulator 27, so that the pin 24 at the free end of the piston rod is moved to the position indicated by the numeral 24a, the pin 19 is also moved to the position indicated by the numeral 19a, whereby the torque shaft 9 and hence the left bucket shell 7 are caused to rotate in the clockwise direction through an angle AOB The center of the pin 18 on the lever 16 is caused to move to the position indicated by the numeral 180 because the lever 16 is coupled by the connecting rod 17 to the lever 13 so that the torque shaft 10 and hence the right bucket shell 8 are caused to rotate in the counterclockwise direction through an angle AAO'B'. Thus the bucket is opened.

When the pin 24 is returned to its initial position indicated as shown in FIG. 2 from the position 24a as the piston rod 23 of the hydraulic cylinder 20 is extended in the direction b, the bucket shells 7 and 8 are moved toward each other, that is the bucket is closed. The bucket materials are now loaded in the closed bucket as shown in FIG. 1. In this case, if the frictional forces of various moving parts are neglected, the moments of the bucket shells due to the bulk material grabbing forces thereof are equal because L L' as far as the moment of the hydraulic cylinder about the torque shaft 9 exceeds the sum of the moments required for opening or closing the bucket shells 7 and 8. Therefore, the moment of the cylinder 20 is divided depending upon the moments of the grabbing forces about the torque shaft 9.

The hydraulic cylinder 20, the motor 25 and the hydraulic pump 26 are disposed over the center plane CD shown in FIG. 3 of the center frame or head unit 6 or disposed in such a manner that the forces of these parts are symmetrical with respect to the center plane CD. When it is desired that two hydraulic cylinders 20 be incorporated in the apparatus as shown in FIG. 4, the levers l3 and 16, the torque shafts 9 and 10 and the connecting rods 17 are duplicated and are disposed in symmetrical relation with respect to the center plane CD. The levers 13 and 16 and the connecting rod or rods 17 may be solid or may have any suitable cross section In FIG. 5 the hydraulic circuit between the pump 26, the accumulator 27 and the hydraulic cylinder 20 includes an electromagnetically operated switching valve 31, controlled by the solenoids 32 and 33, as will be explained later, and a relief valve 34.

In FIG. 6 the electrical circuit for control of the apparatus includes a control panel 35 having a switch 36 and the control panel 37 includes a timer 38 and a timer 39. The control panel 40 on the motor 25 includes the solenoids 32 and 33.

The cover 30 of the center frame head unit 6 has a waterproof seal and the power cable entrance 41 is also provided with a waterproof seal in well known manner.

Since the bucket shell driving shafts 9 and 10 are supported by the split journals 12 at the four corners of the under surface of the center frame, the dimensions of the head frame unit 6 may be selected independently of the dimensions of the bucket shells and only dependently upon various bucket shell driving mechanisms incorporated within the head frame unit 6.

The distance of the pair of bucket shell driving or torque shafts 9 and 10 is not limited by the working stroke of the hydraulic cylinder 20 so that standardization of the center frame 6 becomes possible and the bucket shells 7 and 8 may be replaced depending upon a desired grab bucket capacity.

The bucket shells 7 and 8, being securely fixed to the torque shafts 9 and 10, form rigid frames when seen from the direction in which the grab bucket is opened and closed so that the bucket hells have sufficient strength to resist lateral forces and are simple in construction and minimum weight.

The bucket shells 7 and 8 may be removed from the center frame by removing one or two hydraulic-cylinder-connecting pins 24 and one or two connecting-rodconnecting pins 18-19 and disassemblying the four split-journals 11, 12 on the under surface of the center frame, one or two pins being dependent upon whether one or two hydraulic cylinders are employed, and the hydraulic cylinder or cylinders are also disassembled in a simple manner only by removing the cylinder mounting pivot pins 21 and hoses coupled to the hydraulic cylinder or cylinders, not shown, whereby the maintenance, inspection and repair may be carried out by a minimum number of workmen within a very short time.

FIG. 7 is a graph illustrating the relationship between the hydraulic cylinder stroke in seconds and the pressure exerted to the closing edges 45 of the bucket shells 7 and 8 under the resistance of the bulk materials grabbed by the grab bucket and the hydraulic pressure of the accumulator 27.

In the instant embodiment, it is assumed that the grab bucket capacity is 0.8m; the discharge of the hydraulic pump 26 is 30 l/min.; the volume of the hydraulic cylinder 20 on the side A of its piston 23a is 3.8 I, while that on the side B of its piston 23a is 2.9 1 (FIG. 5); the relief valve 34 is set at a pressure of l4Okg/cm and 10 I of gas under pressure of kg/cm (G) is sealed in the accumulator 27.

To close the grab bucket, the switch 36 on the operation panel 35 (see FIGS. 5 and 6) is set to CLOSE whereby the timer 38 which is preset to desired time interval is actuated to rotate the electric motor 25. Therefore, the working oil under pressure is discharged from the hydraulic pump 26 which is driven by the motor 25 and the port of the upper valve of switching valve 31 is opened (to the left) as its solenoid 32 on plane 40 is energized urging the lower valve within 31 to the right. The working oils under pressure from both the accumulator 27 and the pump 26 are introduced into the hydraulic cylinder 20 on the side A of its piston 23a from the same hydraulic circuit so that the piston 23a is displaced toward B (FIG. 5). The result is that the piston rod 23 remains extended and the grab bucket closed.

Referring to FIG. 2, the link 17 is connected to the piston rod 23 by the connecting pin 24 and is also connected to the lever 13 by the connecting pin 19. The link 17 is also connected to the lever 16 by the connecting pin 18. The connecting pins 24,- 19 and 18 are displaced from the original positions a, b and when the piston 23a is adjacent the side A (FIG. toward the positions a, b and c' in the direction of the side B (FIG. 5) whereby the bucket shells 7 and 8 are moved toward each other. Thus the bulk materials are grabbed by the grab bucket.

To open the grab bucket the notch 36 is set to OPEN whereby the timer 39 is activated to rotate the electric motor 25. Oil under pressure is discharged from the pump 26 and the port of the upper valve of switching valve 31 is opened (moved to the right) as its solenoid 33 is energized urging the lower valve within 31 to the left. The oil under pressure from both the accumulator 27 and the pump 26 is introduced into the hydraulic cylinder 20 on the side B of its piston 23a so that the piston 23b is displaced towards A (FIG. 5), resulting in the torque shaft 9 being rotated clockwise and the torque shaft being rotated counterclockwise and the grab bucket being opened.

The switching valve 31 and the solenoids 32 and 33 may be operated manually to direct pressure oil from the accumulator 27 only to the hydraulic cylinder in the event that it is found desirable to cut out the motor and pump 26.

From the foregoing description, it is seen that by the present invention, the accumulator which had been used as a damper in the prior art grab bucket, is used together with the pump or used alone as a hydraulic pressure source for actuating the hydraulic cylinder and that the timers for closing and opening the grab bucket are inserted into the electric circuit which has a dual function of operating the switching valve and driving the motor which in turn drives the pump so that both of the time intervals for rotating the motor and for opening the ports of the switching valve may be controlled to thereby adjust the hydraulic pressure in the accumulator. Thus the grab bucket may be repeatedly opened and closed, and the closing operation of the grab bucket is made in conjunction with the lifting speed of the crane or the like whereby the efficiency is much improved. Furthermore, the grab bucket operation is much simplified and carried out by an unskilled operator. The grabbing efficiency is also much enhanced and the grab bucket closing and opening time intervals are much reduced. The hydraulic pressure in the accumulator may be sufficiently recovered during lifting, lowering, travelling, traversing or swinging of the grab bucket so that the small-sized and hence inexpensive motor and pump may be employed. Since power consumption is less, cabtyre cables with a small current carrying capacity, which are readily available in the market, may be used and a drum for winding these cables may be designed, compact in size and light in weight. The closing and opening speeds of the grab bucket may be controlled by the hydraulic pressure in the accumulator. The existing electrically and hydraulically operated grab buckets may be simply modified to incorporate the present invention. The capacities of the hydraulic cylinder and accumulator may be varied depending upon the bucket capacity so that the standardization of the driving parts may be enhanced.

The specific characteristics of the Power Grab above described obtain a significant increase in the quantity of material handled at each grab load. This is because the grabbing efficiency of the grab, unlike the wire operated grab, does not depend upon the weight of the grab. The additional amount of material handled with each cycle, therefore, represents a substantial increase in the quantity of material handled in a given time.

Less skill is required to operate the Power Grab because of its ability to perform efficiently with the bucket inclined. This feature is a significant advantage when digging is performed in deep wells or similar locations. Opening and closing of the grab is performed by a simple lever or push button switch.

The cubic capacity of the grab may be varied over a wide range without reducing the efficiency of the grab. This feature reduces the danger of overloading the hoisting equipment when changing from handling of one material to another and eliminates the need for two or more complete grabs for different materials.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for operating grab buckets and the like comprising a housing, an electric motor, a pump operatively connected to said motor, hydraulic accumulator, and a cylinder and piston device all mounted within the said housing, the said cylinder and piston device being pivotally mounted at one end of the said housing, a pair of torque shafts each mounted in bearings on the under side of said housing and disposed transversely of the axis of the cylinder and piston device, a grab bucket shell mounted on each of said torque shafts, a lever mounted on each of said torque shafts, a first of said levers adjacent to the pivot mounting of the cylinder and piston device being directed downwardly with respect to the said housing and the second of said levers being directed upwardly into the said housing, said second lever having its free end coupled to the free end of the piston rod of the cylinder and piston device, a tie rod connected at one end to the free end of said first lever and having its opposite end connected to said second lever at a position intermediate of its torque shaft and its connection to the said piston rod, hydraulic connections between said pump, accumulator and the cylinder of said cylinder and piston device, means to control the flow of hydraulic fluid to the said cylinder and piston device to effect rotation of said torque shafts in counter direction to each other for opening and closing of the grab bucket shells, said means to control the flow of hydraulic fluid from the said pump including a pair of solenoid valves to control the extension and retraction cycles of the cylinder and piston device, and including a pair of timers controlling the opening and closing of the solenoid valves and the opening and closing cycles of the grab bucket.

2. Apparatus as set forth in claim 1 in which the said tie rod is connected to the respective first and second levers at an equal radius from the axis of the torque shafts on which they are mounted.

3. Apparatus as set forth in claim 1 in which the said cylinder and piston device when extended effects closing of the grab bucket and when retracted effects opening of the grab bucket.

4. Apparatus as set forth in claim 1 in which the said tie rod effects rotation of the torque shafts in directions opposite to each other when the cylinder and piston device is activated in either extending or retracting direc tions.

5. Apparatus as set forth in claim 1 in which the bearings in which the said torque shafts are mounted are of the split type, and the torque shafts and their attached levers and grab bucket shells are detachable from the said cylinder and piston device and the said housing.

6. Apparatus as set forth in claim 5 in which the said grab bucket shells are mounted on the end portions of the torque shafts beyond the adjacent sides of the said housing.

7. Apparatus as set forth in claim 1 in which the said solenoid valves can be manually operated to permit the flow of hydraulic fluid to and from the hydraulic accumulator to the cylinder and piston device.

8. An apparatus for operating grab buckets and the like comprising: a frame, a pair of parallel torque shafts mounted on the frame, a grab bucket shell mounted on each of said torque shafts, a double acting hydraulic piston and cylinder unit mounted on the frame and operatively connected to the grab buckets to open them when moved in one direction and close them when moved in the other direction, pipe means for delivering the output of the pump to either side of the piston and cylinder unit, power means for operating the pump, a switching valve in the pipe means between the pump means and the piston and cylinder unit, said switching valve including a first solenoid means for moving the valve to a first position to deliver hydraulic fluid to a first side of the piston to expand the piston and cylinder unit, and a second solenoid means for moving the valve to a second position to deliver hydraulic fluid to the second side of the piston to retract the piston and cylinder unit, and including a timer means for controlling the opening and closing either of said solenoids and for controlling the duration of operation of the power.

means to operate the pump and hence pump hydraulic fluid towards to said piston and cylinder unit.

9. The apparatus of claim 8 including a hydraulic accumulator in the pipe means between the pump and the switching valve, said timer means being operable to permit the pump to pressurize the hydraulic accumulator when the grab buckets are not being moved, whereby the energy of the hydraulic accumulator is released during the time that the grab buckets are being moved.

10. The apparatus of claim 9, said timer means being adjustable to vary the cycle time of the opening and closing of the grab buckets for different types of loads.

1 1. The apparatus of claim 9, said power means being an electric motor.

12. An apparatus according to claim 9, said piston and cylinder unit being operable to close the buckets together when extended and to open the buckets when retracted.

13. The apparatus of claim 9, including means for manually operating said solenoid valves to permit the flow of hydraulic fluid to and from the hydraulic accumulator to the piston and cylinder unit 14. The apparatus of claim 9, said frame being a housing containing the power means which is an electric motor, said hydraulic accumulator and said hydraulic piston and cylinder unit, the piston and cylinder unit being pivotally connected to the housing, said torque shafts being mounted on the underside of said housing and disposed transversely of the axis of the piston and cylinder unit.

15. The apparatus of claim 14, including a lever fixedly mounted on each torque shaft, a first of said levers adjacent to the pivot mounting of the piston and cylinder unit being directed downwardly with respect to said housing and the second of said levers being directed upwardly into said housing, said second lever having its free end coupled to the free end of the piston rod of the piston and cylinder unit, a tie rod connected at one end to the free end of said first lever and having its opposite end connected to said second lever at a position intermediate of its torque shaft and its connection to said piston rod.

16. The apparatus of claim 15, wherein the tie rod is connected to respective first and second levers at an equal radius from the axis of the torque shafts on which they are mounted.

17. The apparatus of claim 15, wherein the tie rod effects rotation of the torque shafts in directions opposite to each other when the piston and cylinder unit is activated in either the extending or the retracting directions.

18. The apparatus of claim 15, including bearings mounting said torque shafts being of the split type, the torque shafts and their attached levers and grab bucket shells being attachable from the said piston and cylinder unit and the said housing, and wherein the grab bucket shells are mounted on end portions of the torque shafts beyond the adjacent sides of the housing. 

1. Apparatus for operating grab buckets and the like comprising a housing, an electric motor, a pump operatively connected to said motor, hydraulic accumulator, and a cylinder and piston device all mounted within the said housing, the said cylinder and piston device being pivotally mounted at one end of the said housing, a pair of torque shafts each mounted in bearings on the under side of said housing and disposed transversely of the axis of the cylinder and piston device, a grab bucket shell mounted on each of said torque shafts, a lever mounted on each of said torque shafts, a first of said levers adjacent to the pivot mounting of the cylinder and piston device being directed downwardly with respect to the said housing and the second of said levers being directed upwardly into the said housing, said second lever having its free end coupled to the free end of the piston rod of the cylinder and piston device, a tie rod connected at one end to the free end of said first lever and having its opposite end connected to said second lever at a position intermediate of its torque shaft and its connection to the said piston rod, hydraulic connections between said pump, accumulator and the cylinder of said cylinder and piston device, means to control the flow of hydraulic fluid to the said cylinder and piston device to effect rotation of said torque shafts in counter direction to each other for opening and closing of the grab bucket shells, said means to control the flow of hydraulic fluid from the said pump including a pair of solenoid valves to control the extension and retraction cycles of the cylinder and piston device, and including a pair of timers controlling the opening and closing of the solenoid valves and the opening and closing cycles of the grab bucket.
 2. Apparatus as set forth in claim 1 in which the said tie rod is connected to the respective first and second levers at an equal radius from the axis of the torque shafts on which they are mounted.
 3. Apparatus as set forth in claim 1 in which the said cylinder and piston device when extended effects closing of the grab bucket and when retracted effects opening of the grab bucket.
 4. Apparatus as set forth in claim 1 in which the said tie rod effects rotation of the torque shafts in directions opposite to each other when the cylinder and piston device is activated in either extending or retracting directions.
 5. Apparatus as set forth in claim 1 in which the bearings in which the said torque shafts are mounted are of the split type, and the torque shafts and their attached levers and grab bucket shells are detachable from the said cylinder and piston device and the said housing.
 6. Apparatus as set forth in claim 5 in which the said grab bucket shells are mounted on the end portions of the torque shafts beyond the adjacent sides of the said housing.
 7. Apparatus as set forth in claim 1 in which the said solenoid valves can be manually operated to permit the flow of hydraulic fluid to and from the hydraulic accumulator to the cylinder and piston device.
 8. An apparatus for operating grab buckets and the like comprising: a frame, a pair of parallel torque shafts mounted on the frame, a grab bucket shell mounted on each of said torque shafts, a double acting hydraulic piston and cylinder unit mounted on the frame and operatively connected to the grab buckets to open them when moved in one direction and close them when moved in the other direction, pipe means for delivering the output of the pump to either side of the piston and cylinder unit, power means for operating the pump, a switching valve in the pipe means between the pump means and the piston and cylinder unit, said switching valve including a first solenoid means for moving the valve to a first position to deliver hydraulic fluid to a first side of the piston to expand the piston and cylinder unit, and a second solenoid means for moving the valve to a second position to deliver hydraulic fluid to the second side of the piston to retract the piston and cylinder unit, and including a timer means for controlling the opening and closing either of said solenoids and for controlling the duration of operation of the power means to operate the pump and hence pump hydraulic fluid towards to said piston and cylinder unit.
 9. The apparatus of claim 8 including a hydraulic accumulator in the pipe means between the pump and the switching valve, said timer means being operable to permit the pump to pressurize the hydraulic accumulator when the grab buckets are not being moved, whereby the Energy of the hydraulic accumulator is released during the time that the grab buckets are being moved.
 10. The apparatus of claim 9, said timer means being adjustable to vary the cycle time of the opening and closing of the grab buckets for different types of loads.
 11. The apparatus of claim 9, said power means being an electric motor.
 12. An apparatus according to claim 9, said piston and cylinder unit being operable to close the buckets together when extended and to open the buckets when retracted.
 13. The apparatus of claim 9, including means for manually operating said solenoid valves to permit the flow of hydraulic fluid to and from the hydraulic accumulator to the piston and cylinder unit.
 14. The apparatus of claim 9, said frame being a housing containing the power means which is an electric motor, said hydraulic accumulator and said hydraulic piston and cylinder unit, the piston and cylinder unit being pivotally connected to the housing, said torque shafts being mounted on the underside of said housing and disposed transversely of the axis of the piston and cylinder unit.
 15. The apparatus of claim 14, including a lever fixedly mounted on each torque shaft, a first of said levers adjacent to the pivot mounting of the piston and cylinder unit being directed downwardly with respect to said housing and the second of said levers being directed upwardly into said housing, said second lever having its free end coupled to the free end of the piston rod of the piston and cylinder unit, a tie rod connected at one end to the free end of said first lever and having its opposite end connected to said second lever at a position intermediate of its torque shaft and its connection to said piston rod.
 16. The apparatus of claim 15, wherein the tie rod is connected to respective first and second levers at an equal radius from the axis of the torque shafts on which they are mounted.
 17. The apparatus of claim 15, wherein the tie rod effects rotation of the torque shafts in directions opposite to each other when the piston and cylinder unit is activated in either the extending or the retracting directions.
 18. The apparatus of claim 15, including bearings mounting said torque shafts being of the split type, the torque shafts and their attached levers and grab bucket shells being attachable from the said piston and cylinder unit and the said housing, and wherein the grab bucket shells are mounted on end portions of the torque shafts beyond the adjacent sides of the housing. 